1. Field of the Invention:
The present invention relates to an ink jet recording head having grooves of ink flowing paths and a method of production thereof, more particularly, it relates to an ink jet recording head and a method of production thereof which are applied to a printer, and a duplicating machine, etc.
2. Description of the Related Art:
A conventional ink jet recording head is described in Japanese Laid-Open Patent Publication No. 6-246913 published on Sep. 6, 1994. Referring to FIG. 5, the conventional ink jet recording head is explained. This figure is a cross sectional view illustrating the structure of the conventional ink jet recording head. The head as illustrated in the figure has a structure in which a piezo-electric ceramic element 11 provided with a plurality of grooves 22 and subjected to a polarization treatment in the direction of an arrow 14 is bonded, through a bonding layer 13 of an epoxy based adhesive, to a cover plate 12 of a ceramic material or a resinous material and so on. According to the above constitution, a plurality of the grooves 22 are formed for serving as ink flowing paths. Each ink flowing path is long and narrow in shape and oblong in a cross section, and a side wall 21 is extended over a whole length of the ink flowing path.
An metal electrode 23 for generating a driving electric field is formed on both of the side surfaces of the side wall 21, ranging from the upper portion of the side wall 21 near the adhesion layer 13 on the top of the side wall 21 to the middle portion thereof. Also, a protective layer 30 is formed for covering the electrode 23. Every ink flowing path is filled with ink.
Next, a method of producing the conventional head will be explained. First, the piezo-electric ceramic element 11 is provided with a groove 22 by a cutting work utilizing a thin disk-shaped diamond blade. The metal electrode 23 is formed on an inner side wall of the groove by a sputtering method and so on. Further, the protective film 30 is so made on the inner wall of the groove 22 as to cover the electrode 23.
In a ink jet recording head having such a structure, at the time of being driven, the metal electrodes 23d and 23g are ground and a positive voltage is applied to the metal electrodes 23e and 23f. Then, the direction of an electric field generated by the application of the voltage and the direction of a polarization thereby in each of the side walls 21b and 21c are positioned rectangularly with each other. Accordingly, the side walls 21b and 21c are deformed each toward the inside of the groove 22b through a piezo-electric thickness slide effect. As a result, the ink within the groove 22b is pressurized so that the ink is jetted from a nozzle not shown in any figures.
There are the following problems in an ink jet recording head having such a structure that some grooves are formed on a piezo-electric element by a cutting work and the resulting side walls of the grooves are driven to thereby jet each ink in the grooves.
That is to say, the strength of the side wall is weak because fine cracks are produced in the outer surface of the side wall of the groove by a cutting work, and the cracks are developed further to ends in destroying the side wall or causing the like while the side wall is driven for a long time, which brings a problem in reliability. On the other hand, if a width of the side wall is enlarged in order to reduce the bad influence attributable to the cracks, an interval between the grooves becomes so large as not to allow the nozzles connected the grooves to be disposed in high density.
In another aspect, there is a large surface roughness in the side wall surface which is a surface obtained by subjecting a piezo-electric ceramic substrate to a cutting work. Therefore, the convex portions in the side wall surface are coated with the electrode material and the protective film, however, the concave portions therein have the difficulty to be coated therewith. If the electrode does not contact sufficiently with a piezo-electric ceramic substrate, it decreases an amount of deformation of the side wall. In the case that a coating of the protective film is insufficient, an insulation resistance of the protective film is so lowered as to bring about such defects as an electric current leak into ink and a corrosion of the electrode.
The invention is made to overcome the above disadvantages of the prior art, the object of the present invention is to provide an ink jet recording head in which the strength of the side wall is high and a surface roughness of the side wall is small, and a method of producing the same.